SEC Form 4 explained: how US insider filings work

Who must file Form 4

Section 16(a) of the Securities Exchange Act of 1934 applies to three categories of people at companies with a class of equity registered under Section 12:

• Directors of the issuer.
• Officers, as defined in Rule 16a-1(f): the president, principal financial officer, principal accounting officer, any vice-president in charge of a principal business unit or function, and any other person who performs policy-making functions.
• Beneficial owners of more than 10 percent of a registered class of equity securities.

Beneficial ownership under Rule 16a-1 reaches through the legal wrapper: securities held by immediate family sharing the household, by trusts, and by controlled entities can count toward the insider's position. That is why a single Form 4 sometimes lists shares held "indirectly" by a spouse, a family LLC, or a foundation.

Three forms cover the lifecycle. Form 3 is the initial statement of holdings, due within 10 days of becoming an insider. Form 4 reports changes in ownership. Form 5 is an annual catch-up, due within 45 days of fiscal year end, for the narrow set of transactions eligible for deferred reporting.

What transactions get reported

Form 4 covers changes in beneficial ownership: open-market purchases and sales, awards and grants from the issuer, option exercises and conversions, dispositions back to the issuer, and, since the 2023 amendments, bona fide gifts. Derivative positions (options, warrants, convertible notes) are reported in their own table with strike, expiry, and the underlying share count.

Transaction codes that matter

Every line carries a one-letter transaction code from the SEC's official list. The codes an investor should know:

A screen that does not separate P and S from the rest is counting payroll, not conviction.

The two business day deadline

Before August 2002, insiders had until the 10th day of the following calendar month, a lag of up to 40 days. Section 403 of the Sarbanes-Oxley Act rewrote Section 16(a) to require filing "before the end of the second business day following the day on which the subject transaction has been executed". Form 3 keeps its 10-day clock, Form 5 its 45-days-after-fiscal-year-end clock.

The 2-day rule makes US insider data the fastest of any major market. MAR Article 19 in the EU allows 3 business days from the transaction, Canada allows 5 calendar days for subsequent reports, and Japan's officer reports run on a monthly cycle. For event studies anchored on the filing date, that difference is not cosmetic: it changes how much of the move you have already missed.

Where filings are published

Everything lands on EDGAR, the SEC's disclosure system, at sec.gov. Access is free, with no registration. Three practical entry points:

• Full-text search (the EDGAR search UI, covering filings since 2001) filtered to form type 4.
• Per-issuer browse pages listing every ownership filing.
• Official JSON APIs at data.sec.gov, no authentication or API key required, plus the forms themselves disseminated as structured XML.

That last point explains why the US insider ecosystem is so much deeper than anywhere else. Nobody has to parse PDFs.

Late filers get named in public too: Item 405 of Regulation S-K forces issuers to list delinquent Section 16 filers, with the number of late reports, under "Delinquent Section 16(a) Reports" in the annual proxy statement.

How to read a Form 4

A Form 4 has a fixed layout. The fields that carry signal:

• Reporting person and relationship boxes: Director, Officer (with title), 10% Owner, Other. One filing can tick several.
• Table I (non-derivative securities): the security, transaction date, transaction code, shares acquired (A) or disposed (D), price, and shares owned following the transaction, split by direct and indirect ownership.
• Table II (derivative securities): options, RSUs, warrants, with exercise price, exercisability dates, and underlying share counts.
• The 10b5-1 checkbox: ticked when the trade was executed under a pre-arranged Rule 10b5-1 plan, with the plan adoption date.
• Footnotes: where the real story often hides. Pricing formulas, plan details, trust arrangements, and the reason a "sale" is actually a tax-withholding event all live in the footnotes.

Read the code first, the footnotes second, the headline share count last.

Interpretation traps

10b5-1 plans are pre-scheduled, not reactive

A sale executed under a Rule 10b5-1 plan was scheduled months in advance, when the insider adopted the plan. Since the SEC's December 2022 amendments (effective February 27, 2023, with the form changes mandatory from April 1, 2023), directors and officers face a cooling-off period running to the later of 90 days after plan adoption or two business days after the issuer files the 10-Q or 10-K covering the quarter of adoption, capped at 120 days. The Form 4 checkbox now makes these trades identifiable, though a ticked box only asserts the plan is intended to qualify. Treating a plan sale as a bearish signal on the filing date misreads the timeline.

Option exercises are not buying

A code M exercise followed by a code S sale on the same day is a cashless exercise: the insider monetised compensation. The M line looks like an acquisition. It is not a purchase decision at the current price.

Code F is payroll, not selling

When shares vest, issuers routinely withhold a slice to cover the tax bill. That surrender is reported with code F and looks like a disposition. It says nothing about the insider's view of the stock.

Gifts now move fast

Bona fide gifts (code G) historically could wait for the annual Form 5. The 2023 amendments moved gifts of securities onto Form 4's 2-day clock, after academic work showed strategically timed gifts around private information.

The 10 percent owner is often a fund

Activist funds and large asset managers cross the 10 percent line and become Section 16 filers. Their Form 4s are portfolio management, not insider knowledge of operations. Role filtering matters as much as code filtering.

How insiders-trades.com tracks SEC Form 4

We ingest Form 4 filings from EDGAR's full-text search API daily and backfill history month by month, parsing the structured XML rather than the rendered pages. Each filing becomes a declaration row with the transaction code preserved, the role normalised (CEO, CFO, board member, 10 percent owner), and amounts converted to EUR for cross-market comparison. Discretionary codes (P, S) drive scoring; compensation codes are ingested but weighted accordingly.

Browse the live output on the US market hub, or start from a company page such as Alphabet or CrowdStrike. For a sense of how prolific a single Section 16 filer can be, see the filing history of Murray Stahl, one of the most frequent Form 4 filers in the entire dataset.

For the EU equivalent of this regime, see our MAR Article 19 guide, and for how the rest of the world compares, the insider disclosure rules by country index.